Actuators are currently available in multiple varieties including electric ballscrew actuators, electric threaded rod actuators and Electric Hydraulic Actuators (EHAs).
According to one currently available EHA design an EHA includes a hydraulic cylinder unit with a fully encapsulated hydraulic supply system comprising a reservoir, check valves and relief valves, and a hydraulic pump, which is powered by an electric motor. The reservoir includes a volume of compressed gas separating the gas from the hydraulic fluid and allowing for orientation independent operation of the unit. In general, when the electric motor is driven in a first rotational direction, the hydraulic pump moves the fluid into the fluid chamber of the hydraulic actuator and out of the piston chamber, thereby extending a piston rod from the actuator housing. When the electric motor is driven in a second rotational direction, opposite the first rotational direction, the hydraulic pump moves the hydraulic fluid out of the fluid chamber and into the piston chamber, thereby retracting the rod.